"vapor mode" explainer & getCurrentInstance prep

[43081j]

For those of us maintaining popular vue packages (vueuse in my case), we could do with a proper explainer doc of "vapor mode" that goes beyond what the various changelogs and blog posts mention.

similarly, the reason i'm looking for this is that getCurrentInstance will now be null in vapor components. nothing seems to explain why this is, though.

the explanation of how vapor works (or what it is) will probably make that obvious. i'd rather understand the architecture than this individual change.

this particular change will break a lot of libraries when people try use them with vapor set. so it would be good if each of those major changes had migration info, at least.

[abdullah-wn]

I wonder too because vapor components have an instance attached to them, this instance is used when for lifecycle hooks (onMounted, onUpdated, etc...) and getCurrentInstance is especially set to return null on vapor component

export const getCurrentInstance: () => ComponentInternalInstance | null = () =>
  currentInstance && !currentInstance.vapor
    ? (currentInstance as ComponentInternalInstance) // exist but skip on vapor mode
    : currentRenderingInstance // never set on vapor component